| 摘要 |
PROBLEM TO BE SOLVED: To improve the accuracy of detection value by improving the temperature characteristics of a toner density sensor. SOLUTION: This sensor is provided with a driving coil 1 connected to an oscillator 5, a reference coil 2 and a detecting coil 3 electromagnetically coupled to the coil 1, and toner density is detected by using differential output between the coils 2 and 3. A capacitor 8 and a variable capacitance diode 9 are connected between an intermediate terminal 13 provided between the coils 2 and 3 and a grounded end 10. A compensating capacitor 12 having temperature characteristics equal to that of the capacitor 8 is connected in parallel with the coil 2. Thus, the temperature characteristics on a coil 2 side are made equal to that to the coil 3 side, so that the influence of the temperature characteristics on the coil 3 side can be cancelled. |
